One Rep Max Calculator
Testing a true one-rep max is risky and takes a full session. Estimating it from a set of five is safer, almost as accurate, and something you can do every week.
The four formulas
They agree closely at low rep counts and diverge as reps climb. Brzycki tends to read lower at high reps; Epley reads higher. Averaging them, as this calculator does, is a reasonable hedge, and the spread between them is itself a useful signal: when it is wide, the estimate is soft.
All of them assume the set was taken close to muscular failure. A set of five with three reps left in reserve is really a set of eight, and the estimate will be correspondingly low.
Where the estimate is trustworthy
Accuracy is best in the 3–8 rep range, where these equations sit within about 5 % of a tested maximum. Outside it the assumptions degrade:
- Above 10 reps the result depends far more on muscular endurance than on maximal strength, and individual variation becomes large. Two lifters with the same true 1RM can differ by five reps at 70 %.
- Exercise matters. The equations were developed largely on bench press. They transfer reasonably to squat and press, less well to deadlift — where most lifters manage fewer reps at a given percentage — and poorly to isolation movements.
- Training history matters. Novices typically achieve fewer reps at a given percentage than experienced lifters, who have learned to sustain effort near their limit.
Using the percentages
Most strength programmes are written as percentages of 1RM, which is the main practical reason to know yours:
| % of 1RM | Typical reps | Primary adaptation |
|---|---|---|
| 90–100 % | 1–3 | Maximal strength, neural |
| 80–90 % | 3–6 | Strength with some size |
| 70–80 % | 6–12 | Hypertrophy |
| 60–70 % | 12–20 | Endurance, technique work |
Re-estimate every four to six weeks rather than every session: day-to-day performance swings with sleep, stress and nutrition, and chasing a new maximum weekly is how people get hurt. Many coaches now prefer autoregulation — using reps in reserve or bar speed — precisely because a fixed percentage ignores how you actually feel that day.
Frequently asked questions
Should I test a true one-rep max?
Rarely, and only with solid technique, a proper warm-up and a spotter or safety bars. For most people the estimate is close enough, and the injury risk plus the recovery cost of a genuine maximal attempt is not worth the extra precision. Competitive lifters testing in the final weeks before a meet are the exception.
Why is my deadlift estimate too high?
Deadlifts typically allow fewer reps at any given percentage than bench or squat — the range of motion is long, there is no stretch-shortening cycle from the floor, and grip and lower back fatigue accumulate fast. Many lifters find Brzycki fits the deadlift better than the average.
Does bar speed matter?
It is arguably a better guide. Velocity-based training uses the speed of the bar to infer proximity to maximum in real time, which accounts for how you feel today in a way a fixed percentage cannot. It needs a tracking device, but it is the more precise approach.